Doe anyone know how to increase the brightness of a multiple page pdf for print quickly?
Print settings don't seem to do it. I just want to print at like 80-90%. Is this possible in acrobat?

hope, I understood your problem right, but at most of my digital-prints, I reduce black for -10 %, directly on the printer-settings...

create an action in Photoshop to import, darken and resave?

You can't adjust the brightness of the PDF file itself. If you have Acrobat Professional, you can edit each element (vectors in AI, rasters in PS).

Printing lighter should be a function of the Printer Driver (Printer Properties).

Also, try using a different output color profile for printing (Print - Advanced)
The default is usually Printer/PostScript Color Management. Test different ones to see how they affect the printed output (that will mess your printed colors, of course) E.g. if you're printing b/w, selecting "Dot Gain 30%" will print lighter than "Dot Gain 10%"

Ideally, you should use a printer-profile package (software + scanner) to build a color profile for your particular printer and tweak it until you get the right result.

Am guessing your best bet is to create the doc lighter before you PDF it...? Or open the PDF page by page in PS (yawn)!!!